WASHINGTON (States News Service) -- Scientists who study Earth's atmosphere may soon have a new way to reach into thin air -- pumpkin-shaped balloons.

In response to problems with longevity and costs associated with balloons and satellites, NASA is developing the next generation of research balloons that can stay aloft for up to 100 days at a fraction of the cost of a space launch.

The initiative – dubbed the Ultra-Long Duration Balloon project (ULDB) – combines an unconventional design with a new type of material for the balloon’s skin. The result is a craft that can stay aloft longer and carry heavier loads than its conventional counterparts.

A researcher inspects a model of the new balloon. (Credit: NASA)

Rather than use the spherical design of conventional balloons, the NASA team behind the ULDB decided to try a pumpkin-like shape. The new design allows the weight of the payload to be carried by the cables that connect the cargo to the balloon, rather than by the balloon itself. Because the balloon is not actually doing the lifting, the NASA design team was able to use a thinner material for the balloon’s skin and allow for heavier loads.

"With the pumpkin, what we do is cheat Mother Nature a little bit," said ULDB project manager Steve Smith.

Though the balloon’s ultrastrong skin is made up of three separate layers of material, it is only as thick as a sheet of plastic wrap. The inner and outer layers are made up of low-density polyethylene film, which allows the balloon to stretch to changes in the helium’s density. The middle layer is made of high-density polyethylene film to give the skin strength, Smith said.

The ideas behind the ULDB’s design are not new – scientists have been toying with various models for a long-duration lighter-than-air craft for years, Smith said. It was the development of the polyethylene film and the success of the pumpkin design, though, that took the design off paper and into the sky.

"The technology and materials have finally caught up with the concept," he said.

NASA launched a prototype model of the balloon in early June over the New Mexico desert to test the design and materials involved in the $13 million project. Smith said the 30-hour test was a success. "We were very ecstatic and happy," he said.

When the full-size balloon is completed, it will be about 20 million cubic feet (565,000 cubic meters) – about the size of a football stadium – and able to carry payloads as heavy as 3,500 pounds (1,585 kilograms) at heights of up to 115,000 feet (35,000 meters). Smith expects the full-size balloon to enter its first round of drills by the end of the year.

The gigantic balloon’s first payload, set for launch in December 2001 from New Zealand, will be the Trans-Iron Galactic Element Recorder. TIGER aims to examine particles from cosmic rays and help scientists discover the origin of the material that makes up the rays, said Paul Hink, a professor of physics at Washington University in St. Louis, where TIGER is based.

"It was a very nice solution for us, as it was a very nice solution for a lot of scientific investigations that are similar to ours," Hink said. "There are lots and lots of programs that are going to be very successful with ULDB projects."

Jason Link, a Washington University graduate student, said that the balloon’s 100-day flight lengths make it ideal for the TIGER experiment because the cosmic-ray particles that the TIGER will look for are so rare.

NASA hopes that this new generation of balloons will be used for a variety of purposes – from atmospheric and space exploration to defense and commercial uses, even for possible launch from other planets. Smith said that there is already discussion about a second-generation ULDB, one that could stay aloft for as long as 1,000 days.

"This is the first generation of these things," Smith said. "There’s a lot of things we can do to improve the design."